Klein Tunneling of Gigahertz Elastic Waves in Nanoelectromechanical Metamaterials

TL;DR

This paper demonstrates acoustic Klein tunneling at gigahertz frequencies in nanoelectromechanical metamaterials, showing near-perfect wave transmission through barriers, with potential applications in classical and quantum waveguiding.

Contribution

It is the first experimental realization of acoustic Klein tunneling in nanoelectromechanical systems operating at gigahertz frequencies.

Findings

Near-unity transmission in Klein tunneling regime

Frequency-dependent transmission consistent with microwave analysis

Angular control of wave transmission

Abstract

Klein tunneling, the perfect transmission of a normally incident relativistic particle through an energy barrier, has been tested in various electronic, photonic, and phononic systems. Its potential in guiding and filtering classical waves in the Ultra High Frequency regime, on the other hand, has not been explored. Here, we report the realization of acoustic Klein tunneling in a nanoelectromechanical metamaterial system operating at gigahertz frequencies. The piezoelectric potential profiles are obtained by transmission-mode microwave impedance microscopy, from which reciprocal-space maps can be extracted. The transmission rate of normally incident elastic waves is near unity in the Klein tunneling regime and drops significantly outside this frequency range, consistent with microwave network analysis. Strong angular dependent transmission is also observed by controlling the launching angle of the emitter interdigital transducer. This work broadens the horizon in exploiting high-energy-physics phenomena for practical circuit applications in both classical and quantum regimes.